Reduction in stillbirths at term after new birth induction paradigm: results of a national intervention

Abstract

Objective: The risk of fetal death increases steeply after 42 gestational weeks. Since 2009, Denmark has had a more proactive policy including prevention of prolonged pregnancy, and early intervention in women with diabetes, preeclampsia, high body mass index and of a higher age group. The aim of this study was to describe the development in fetal deaths with this more proactive birth induction practice, and to identify and quantify contributing factors for this development.

Design: National cohort study.

Setting: Denmark.

Participants: Delivering women in Denmark, 1 January 2000 to 31 December 2012.

Outcome measures: Stillbirths per 1000 women at risk (prospective risk of stillbirth) and per 1000 newborn from 37 and 40 gestational weeks, respectively, through the study period.

Results: During the study period, 829,165 children were live born and 3770 (0.45%) stillborn. Induction of labour increased from 12.4% in year 2000 to 25.1% in 2012 (p<0.001), and the percentage of children born at or after 42 weeks decreased from 8.0% to 1.5% (p<0.001). Through the same period, the prospective risk of stillbirth after 37 weeks fell from 0.70 to 0.41/1000 ongoing pregnancies (p<0.001), and from 2.4 to 1.4/1000 newborn (p<0.001). The regression analysis confirmed the inverse association between year of birth and risk of stillbirth. The lowest risk was observed in the years 2011-2012 as compared with years 2000-2002 with a fully adjusted HR of 0.69 (95% CI 0.57 to 0.83). The general earlier induction, the focused earlier induction of women with body mass index >30, twins, and of women above 40 years and a halving of smoking pregnant women were all independent contributing factors for the decrease.

Conclusions: A gradually more proactive and differential earlier labour induction practice is likely to have mainly been responsible for the substantial reduction in stillbirths in Denmark.

Keywords: EPIDEMIOLOGY; OBSTETRICS.

Figure 1

Proportion (%) of induced deliveries and of children born from 41 and 42 weeks, respectively, in Denmark from 2000 to 2012. Number of children born: 832 935.

Figure 2

Fetal deaths per 1000 ongoing pregnancies according to gestational age during the periods 2000–2008 and 2009–2012. Number of weeks: 3 406 615. Number of fetal deaths: 3770. Lower part the same in a semilogarithmic plot.

Figure 3

Crude fetal deaths per 1000 ongoing pregnancies according to gestational age during the period 2000–2012 and after adjustment for different confounders. *Lower part the same in a semilogarithmic plot.

Figure 4

Fetal deaths per 1000 ongoing pregnancies (upper), and per 1000 newborn (lower) after 37 and 40 gestational weeks, respectively, in different subperiods from year 2000 to 2012. 95% confidence limits indicated.